Solar battery calculator: is a battery worth it for you?
Compare panels only with a 5 kWh and a 10 kWh battery. You'll see the extra cost, the extra savings and which option pays back best over 25 years.
Prices updated October 2026
- Your home
- Your roof
- Energy use
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How a battery changes your savings
Solar panels produce most of their power around midday, when many homes are empty. Without a battery, that spare power is exported for around 12p per kWh. With a battery, you store it and use it in the evening instead of buying power at 26.32p.
A battery also earns money in winter, when panels make less. On a smart tariff it charges overnight at around 8.5p per kWh and runs your home through the expensive daytime and evening hours.
Rule of thumb: each kWh moved from export to self-use is worth about 14.32p more. A 5 kWh battery that fills most days moves 1,000 to 1,400 kWh a year.
Choosing a battery size
| Battery | Typical cost | Usually suits |
|---|---|---|
| 5 kWh | £3,000 | 2 to 3 bed homes, 6 to 10 panels |
| 10 kWh | £5,000 | Larger homes, EV owners, smart tariff users |
| 13 kWh+ | £6,000+ | Heat pump homes and very high usage |
Installed price when fitted at the same time as panels, including 0% VAT.
Frequently asked questions
Is a solar battery worth it?
Usually, if you're out during the day or can use a smart tariff. Without a battery most homes use 30 to 50% of their solar power. A battery lifts that to 70 to 90% and lets you buy cheap overnight power in winter. Payback is often similar to panels alone, but total savings over 25 years are higher.
What size solar battery do I need?
A common rule is a battery roughly equal to your average evening and overnight use. Many 3-bed homes use 5 to 8 kWh after dark, so a 5 kWh battery suits most. Homes with an EV, heat pump or high usage benefit from 10 kWh or more.
How much does a solar battery cost?
A 5 kWh battery typically costs around £3,000 installed alongside panels, and a 10 kWh battery around £5,000. Adding a battery to an existing system costs a little more because it needs its own installation visit.
Can I add a battery to my existing solar panels?
Yes. Most systems can take an AC-coupled battery, which connects without changing your existing inverter. It's a popular upgrade for homes on older export rates.
How long do solar batteries last?
Most lithium iron phosphate (LFP) batteries are warrantied for 10 years or 6,000 cycles and keep at least 70% of their capacity at the end of the warranty.
Does a battery work in a power cut?
Only if it has a backup or off-grid function. Many batteries switch off with the grid for safety. If backup matters to you, ask your installer for a model with an emergency power supply.
Get a battery and panel quote
Book a free survey and an installer will size the battery to your actual usage.